106 PHYSIOLOGICAL CHEMISTRY. 



especially in the saliva, bile, vaginal fluid, tears, nasal mucus, 

 etc. The amount present, however, is always small and the 

 separation very difficult in pure condition. The mucin of the 

 submaxillary gland is probably the best known. 



These bodies contain one of the complex protein groups, 

 since they give the reaction with Millon's reagent, the xantho- 

 proteic and the biuret reactions. They are only 'slightly solu- 

 ble in water and in presence of alkali produce a viscous stringy 

 liquid which is extremely characteristic, even in great dilu- 

 tion. On warming with dilute alkali the viscous condition 

 disappears through formation of alkali albuminate. On treat- 

 ment with strong alkali or superheated steam a peculiar body 

 is formed which, from its discoverer, is known as Landwehr's 

 animal gum. This is now known to contain the protein and 

 carbohydrate complexes; after diluting with weak acid and 

 boiling the sugar reaction may be easily obtained. 



The mucins are much more resistant than the nucleo- 

 proteids against the action of reagents or ferments, but they 

 undergo both peptic and pancreatic digestion slowly. In 

 urine the identification of mucin is often a matter of impor- 

 tance, as it is frequently mistaken for albumin. The detec- 

 tion of mucin depends on the behavior with cold dilute acetic 

 acid and also on the solubility in hot water after precipitation 

 with strong alcohol. Albumin is permanently coagulated but 

 mucin not. 



Mucoid Bodies. These substances are found in the ten- 

 dons, cartilage, the vitreous body of the eye, the cornea and 

 elsewhere, and are closely related to the mucins. They have 

 the viscous properties of the latter but in general, in concen- 

 trated condition, form stiffer jelly-like masses. The cornea 

 and sclerotic coat of the eye are made up largely of mucoids 

 and collagen dissolved in water. 



The mucoids from tendon have been the most thoroughly 

 studied. An extract is made by prolonged treatment with 

 weak lime-water. The solution is precipitated by acetic acid 

 and the precipitate taken up with ammonia. These operations 



